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Chlamydia trachomatis, TMA

Test code(s) 11361, 15031

Question 1. What is Chlamydia trachomatis and what infection does it cause?

Chlamydia trachomatis is a non-motile, gram-negative, obligate, intracellular bacterium that causes chlamydia infection.Chlamydia is the most commonly reported sexually transmitted infection (STI) in the United States. In 2011, 1,412,791 cases of chlamydia were reported to CDC, but an estimated 2.86 million infections occur annually. A large number of cases are not reported, because most people with chlamydia do not have symptoms. Chlamydia is most common among young people. It is estimated that 1 in 15 sexually active females aged 14-19 years has chlamydia.1

Question 2. Who is at risk for chlamydia, and how is the infection transmitted?

All sexually active people are at risk for chlamydia, since the bacteria is transmitted via anal, vaginal, or oral sex. A combination of biological and behavioral factors contribute to the high incidence in young people. Chlamydia can also be spread from a woman to her baby during childbirth.

Question 3. What are the symptoms of Chlamydia trachomatis infection?

C trachomatis infections are often asymptomatic in both males and females. Symptomatic individuals may present with urethritis, epididymitis, proctitis, cervicitis, acute salpingitis, and pelvic inflammatory disease (PID). Children born to infected mothers are at significantly higher risk for inclusion conjunctivitis and chlamydial pneumonia.

Repeat infections increases a woman's risk of serious reproductive health complications, including PID and ectopic pregnancy.

Question 4. Who needs to be tested for Chlamydia trachomatis infection?

The following people should be tested2-4:

  • Symptomatic individuals
  • Sex partners of infected individuals
  • All sexually active women ≤25 years of age
  • All pregnant women (1st prenatal visit)
  • Pregnant women ≤25 years of age (3rd trimester)
  • Pregnant women at high risk (see below) (3rd trimester)
  • Women and teens attending STI, family planning, or prenatal clinics
  • Women with a previously diagnosed STI
  • Women in high-prevalence settings
  • Women undergoing elective abortion
  • Women residing in detention facilities
  • Women with new or multiple sex partners
  • Women with inconsistent or incorrect use of barrier protection
  • Women being evaluated for infertility

Since most C trachomatis infections are asymptomatic, they are usually discovered through screening programs. The CDC recommends annual chlamydia screening of sexually active women aged ≤25 years. Screening programs can reduce both the prevalence of C trachomatis infection and the rates of  PID in women. Among women, the primary focus of chlamydia screening efforts should be to detect chlamydia and prevent complications.5   

Although evidence is insufficient to recommend routine screening for C trachomatis in sexually active young men, screening those in clinical settings with a high prevalence (eg, adolescent clinics, correctional facilities, and STI clinics) should be considered.

The National Committee for Quality Assurance has made screening for C trachomatis one of its HEDIS measures. The Healthcare Effectiveness Data and Information Set (HEDIS) is a tool used by more than 90 percent of America's health plans to measure performance on important dimensions of care and service.6 This HEDIS indicator measures the proportion of sexually active females between the ages of 15 and 25 who were screened annually for chlamydia infection.

Question 5. What tests are available for C trachomatis and what are the acceptable specimen types?

Nucleic acid amplification tests (NAATs), cell culture, direct immunofluorescence, EIA, and nucleic acid hybridization tests are available for the detection of C trachomatis. NAATs are the most sensitive.

Acceptable specimens from women include urine, endocervical swabs, and vaginal swabs. Acceptable specimens from men include urine and urethral swabs. Rectal swabs collected from people that engage in receptive anal intercourse can also be submitted.

Question 6. What is the APTIMA® test for C trachomatis and how is it performed?

The APTIMA test (Hologic, Inc.) is an NAAT used by Quest Diagnostics. It combines the technologies of target capture and transcription mediated amplification (TMA). The TMA reaction replicates a specific region of the C trachomatis 16S ribosomal RNA (rRNA) via DNA intermediates. A unique set of primers is used for the target molecule. Detection of the rRNA amplification product (amplicon) is achieved using nucleic acid hybridization. A chemiluminescent labeled DNA probe combines with amplicon to form stable RNA:DNA hybrids. Light emitted from the labeled RNA:DNA hybrids is measured as photon signals in a luminometer, which are reported as relative light units (RLU). The method creates over a billion copies of target RNA. Thus, it is extremely sensitive and markedly decreases false-negative results.7

Question 7. How are specimens collected for the APTIMA® C trachomatis TMA test?

Special collection tubes are used. The transport solution in these tubes releases the rRNA target and protects it from degradation during storage. If the collection tubes are not used, the specimen will be rejected.

Collection tubes include:

  • APTIMA COMBO 2 assay unisex swab collection tube for endocervical, vaginal, anal, throat, and male urethral specimens
  • APTIMA COMBO 2 assay urine collection tube for male and female urine
  • ThinPrep® liquid Pap collection tube
  • SurePath® liquid Pap collection tube

Excess mucus should be removed before endocervical sampling by using the white shaft cleaning swab (discard after use). Submit urine collection tubes within 24 hours of collection.

Question 8. If a patient tests positive, what is the treatment for C trachomatis infection?

The infection can easily be treated and cured with antibiotics. Persons with chlamydia should abstain from having sex for seven days after single-dose antibiotics, or until completion of a seven-day course of antibiotics, to prevent spreading the infection to partners. Repeat infection with chlamydia is common. Persons whose sex partners have not been appropriately treated are at high risk for re-infection.

Infants infected with chlamydia may develop conjunctivitis (infection of the membrane lining the eyelids) and/or pneumonia. Chlamydial infection in infants can also be treated with antibiotics.

Question 9. Is retesting required after chlamydia treatment?

Yes. Women and men with chlamydia should be retested about three months after treatment of an initial infection, regardless of whether they believe that their sex partners were successfully treated.1

Question 10. Should pregnant women be tested and treated for C trachomatis?

Yes. Untreated chlamydial infection has been linked to problems during pregnancy, including preterm labor, premature rupture of the membranes surrounding the fetus in the uterus, and low birth weight.8 The newborn may also become infected as the baby passes through the birth canal. Neonatal (newborn) infections lead primarily to eye and lung infections.

All pregnant women should be tested for chlamydia at their first prenatal visit. Repeat testing in the third trimester should be done for women at high risk. When discovered, chlamydia can be treated with antibiotics that are safe during pregnancy.8

  1. Centers for Disease Control and Prevention. Chlamydia: CDC fact sheet. http://www.cdc.gov/std/chlamydia/STDFact-Chlamydia.htm. Accessed November 21, 2013.
  2. Centers for Disease Control and Prevention. Recommendations and Reports: Sexually transmitted diseases treatment guidelines 2010. MMWR. 2010:59(RR-12).
  3. Centers for Disease Control and Prevention (CDC). Summary of notifiable diseases—United States, 2010. MMWR Morb Mortal Wkly Rep. 2012;59:1-111. Erratum in: MMWR Morb Mortal Wkly Rep. 2012 Jul 27;61:562.
  4. Nelson HD, Helfand M. Screening for chlamydial infection. Am J Prev Med. 2001;20(Suppl 3):95-107.
  5. Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2010. Chlamydial infections. http://www.cdc.gov/std/treatment/2010/chlamydial-infections.htm. Accessed November 21, 2013.
  6. National Committee for Quality Assurance. HEDIS and performance measurement. http://www.ncqa.org/tabid/59/Default.aspx. Accessed November 21, 2013.
  7. APTIMA COMBO 2 CT [package insert]. San Diego, CA: Hologic Gen-Probe, Inc; 501799 Rev. A 2009
  8. Centers for Disease Control and Prevention. STDs and pregnancy: CDC fact sheet. http://www.cdc.gov/std/pregnancy/stdfact-pregnancy.htm Page last updated: August 1, 2013
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

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